Chronic functional abdominal pain (CFAP) is the ongoing presence of abdominal pain for which there is no scientific explanation. It is quite similar to, but less common than, Irritable Bowel Syndrome (IBS), and many of the same treatments for IBS can also be of benefit to those with CFAP. The fundamental difference between IBS and CFAP is that in CFAP, unlike in IBS, there is no change in bowel habits such as constipation or diarrhea. Bowel dysfunction is a necessary diagnostic criteria of IBS.

CFAP is characterized by chronic pain, with no physical explanation or findings (no structural, infectious, or mechanical causes can be found). It is theorized that CFAP is a disorder of the nervous system where normal nerve impulses are amplified "like a stereo system turned up too loud" resulting in pain. This visceral hypersensitivity may be a stand-alone cause of CFAP, or CFAP may result from the same type of brain-gut nervous system disorder that underlies IBS. As with IBS, low doses of antidepressants have been found useful in controlling the pain of CFAP.

Non-pharmaceutical approaches to CFAP also overlap with treatments for Irritable Bowel Syndrome. This includes enteric coated peppermint oil capsules, which act as anti-spasmodics to relax the gut and also have pain-killing properties due to the methyl salicylate that naturally occurs in peppermint. Gut-directed hypnotherapy or self-hypnosis can also mitigate the hyperreactive nervous system of CFAP, and help alleviate abdominal pain.